This is a continuation of a project intended to examine the properties of visual pigments of selected vertebrates that have special or unique ecological or phylogenetic relations. To date these pigments have been investigated by the method of extraction in which the physical and chemical properties are studied using standard spectrophotometry. Now it is proposed to study the same pigments while in situ within the cellular environment, thus conferring greater biological relevance to the results. For this purpose a microspectrophotometer will be employed to probe the single cell environment of each pigment. The microspectrophotometer that will be employed is one built by Dr. Ellis R. Loew of Cornell University. This microspectrophotometer is being transferred to UCLA for my use. In this work the isolated outer segments from various vertebrates (geckos, fishes, frog tadpoles, etc.) will be experimentally treated to test the effect, if any, on the spectral properties. The protocols will, at least initially, be dictated by what has already been learned from the extraction method. In the program it is planned to examine the pigments in rods, in cones and in cells that are considered to be transmuted or intermediate type cells. The method of extraction has provided a background for all these cells and now an extension will be made into the more biological realm.